Process of obtaining molybdenum or alloys thereof



UNITED sures? ATENT OFFEQE.

FREDERICK MARK BECKET AND JAMES A. HOLLADAY, OF NIAGARA FALLS, NEW

YORK, ASSIGNORS TO ELECTED METALLURGICAL COMPANY, FALLS, NEW YORK A CORPORATION OF WEST VIRGINIA.

OF NIAGARA.

PROCESS OF OBTAINING MOLYBDENUM OR ALLOYS THEREOF- Io Drawing.

To all whom it may concern:

Be it known that we, g1) Fnnnnmcn M. BECKET and (2) JAMES HOLLADAY, (1) a subject of the King of Great Britain, (2) a citizen of the Umted States, residing at (1) Niagara Falls, (2) Niagara Falls, in the county of Niagara and State of New York, have invented certain new and useful Improvements in Processes of Obtaining Molybdenum or Alloys Thereof, of which the following is a specification.

This invention relates to the production of molybdenum and its alloys, especially ferromolybdenum, and comprises a process whereby a relatively pure molybdenuml product may be prepared from ores or concentrates containing considerable proportions of phosphorus, arsenic, copper and other impurities. According to the invention, the molybdenum-bearing material, usually a wulfenite concentrate, is subjected to a hydrometallurgical treatment with an alkaline reagent, preferably caustic soda or sodium carbonate; the operating conditions being so controlled as to effect a commercially complete transformation of the molybdenum content into sodium molybdate, while as far as practicable restricting the formation of soluble compounds of the more objectionable impurities, including copper, phosphorus, arsenic and vanadium. From the solution thus prepared the molybdenum is recovered in the form of metal or alloys of relatively liigh purity, and preferably of low c'arbomcontent.

The process presents certain variations according-as the initial solvent is the hydroxid or the carbonate of the alkali metal. The variations arise principally from the fact that these compounds, both of which are included in the term alkaline reagent as hereinafter used, differ rather widely in their solvent effect upon lead; Whereas caustic;

alkalies used in the manner described be low dissolve a large proportion of the lead content of the ore, the alkali carbonates have no such effect. Accordingly, when caustic alkali solutions are employed as solvents an appropriate ste for the separation of lead is interpo ated between the leaching of the ore or concentrate and the reduction of the molybdenum compound.

Specification of Letters Patent. Patented Jan. 1'7, 1922. Application filed June 29, 1918. Serial No. 242,563. I

The process will be described by reference to certain specific embodiments thereof, it

being understood that the invention is not limited to the treatment of particular molybdenum ores or concentrates, or to the details of manipulation described by Way of example.

A typical wulfenite concentrate may contain for example:

Molybdenum 10.12 Tungsten 0.70 Vanadium 1.04 Lead 56.53 Iron 3.35 Copper 0.40 Arsenic 0.70 Phosphorus 0.174% Ewample I.

The finely divided concentrate is subjected at normal or if desired at higher temperatures to the action of a rather strong molybdenum content of the ore passed into solution, together with 91% of the tungsten and 82% of the lead, while leaving in. the sludge (separated by filtration) all of the iron and copper, 88% of the'vanadium, 15% of the arsenic and 59% of the phosphorus. It --'will be understood, of course, that the percentage of specific impurities remaimng in the sludge may vary ratherwidely according to the composition and other characteristics of any particular. concentrate treated; and. the above proportions are therefore to be regarded merely as an mdication of the general nature of the results to be expected.

The clear solution, after separatlon from the sludge by filtration or otherwise, may be treated in various ways to recover molybdenum content in reduced form. For example (1) The solution may be evaporated to dryness, the lead removed by smelting'with charcoal or other form of carbon, and the reduction of the molybdenum efiected preferably in an electric furnace, using either silicon (including ferrosilicon) or carbon as the reducing agent, according to whether a low or high carbon product is desired. Iron in the form of turnings or oxid may be added as required in making ferromolybdenum. This direct process is more particularly applicable when the original ores are reasonably low in phos horns and arsenic, or when products exceptionally low 1n phosphorus and arsenic are not requ1red.

(2) The solution may be treated with carbon dioxid or carbonates to precipitate the .lead, and the molybdenum then separately Example 11.

A stron solution of sodium carbonate may be su tituted for caustic soda in the treatment of the concentrates, with the advantage that very little lead passes into solution, rendering it possible to eliminate the special ste s having in view the removal of the lead. is necessary to secure the best results. Satisfactory results are obtained by the use of a saturated solution of sodium carbonate (soda ash) at a temperature of 60 C. or higher, a weight of soda ash used being approximately 15 times the weight of the molybdenum component of the concentrate. In the typical operation of this kind it was found possible to extract substantially all of the molybdenum and tungsten, together with 29% of the vanadium; while all of the iron and copper, 98% of the lead, 14% of the arsenic and 41% of the phosporous remained in the sludg. As in the case of caustic soda it is understood that these extraction percentages may vary within wide limits according to the individual characteristics of the concentrate. An additional advantage possessed by sodium carbonate is its much lesser tendency, as compared with 'ing to the resultin large excess of sodium carbonate modification of the process is hence especially applicable to the treatment of silicious ores and concentrates.

The solutions thus prepared may be evaporated to dryness and smelted for their molybdenum content as described above; or the molybdenum ma be precipitated as the calcium salt, and the latter smelted with silicon or ferrosilicon, or with carbon. In either case iron in suitable form may of course be introduced into the char e, accordgrade of ferromolyb enum desired.

caustic soda, to attack the silicates: this 6| Obviously the processes involving the use of caustic alkalies and their carbonates respectivel might be combined to the extent of leaching the concentrates with mixed caustic and carbonate solutions, with an appropriate after treatment for the separation of any lead which may have been dissolved.

1. In a process of recovering molybdenum from ores or concentrates thereof, the steps which comprise leaching the molybdenumbearing material with an alkaline sodium compound in sufiicient proportion to secure a commercially complete extraction of the molybdenum, while leavin undissolved a substantial proportion of t e impurities of the ore, precipitating molybdenum from the resulting solution as calcium molybdate, and smelting the precipitate.

2. In a process of recovering molybdenum from ores or concentrates thereof the steps which comprise leaching the molybdenumbearing material with an alkaline sodium compound in sufficient proportion to secure a commercially complete extraction of the molybdenum, while leavin undissolved a substantial proportion of t e impurities of the ore, precipitating molybdenum from the solution as vcalcium mol bdate,

and sme ting the precipitate with si icon.

3. In a process of recovering molybdenum from ores or concentrates thereof, the steps which comprise leaching the molybdenumbearing material with a sodium carbonate solution in sufiicient proportion to secure a commercially complete extraction of the molybdenum, while leavin undissolved a substantial proportion of t e impurities of the ore, precipitating molybdenum from the resulting solution as calcium molybdate, and smelting the preci itate.

4. In a process at recovering molybdenum from ores or concentrates thereof, the steps which comprise leaching the molybdenumbearing material with a sodium carbonate solution in sufiicient proportion to vsecure a commercially complete extraction of the molybdenum, while leavin undissolved a substantial proportion of t e impurities of III the ore, precipitating molybdenum from the I I 1,403,477 Y a resulting solution as calcium molybdate, and containing molybdenum, the step which smelting the precipitate with silicon. consists in smelting calcium molybdate, in 10 5. In a process of recovering molybdenum presence of iron, with a reducing agent confrom ores or concentrates thereof, the step taining silicon. I 5 which consists in smelting calcium molybdat'e In testimony whereof, we afiix our sig- .with a reducing agent containing silicon. natures.

6. In a process of preparing low-carbon FREDERICK MARK BECKET. -ferromolybdenum from ores or concentrates JAMES A. HOLLADAY. 

